In a mobile radio communication service such as Long Term Evolution (LTE), LTE-Advanced, and the like (hereinafter collectively referred to as “LTE and the like”), a radio base station device may sometimes include a base band unit (BBU) and a remote radio head (RRH).
A base band unit of a radio base station device may sometimes include an upper-level device and a terminal station device. The upper-level device and the terminal station device may sometimes be integrated in a base station and execute a baseband process.
On the other hand, a remote radio head of a radio base station device is not integrated in a base station and executes a radio process outside the base station. Moreover, the remote radio head is positioned in a lower-level device in relation to an upper-level device and a terminal station device.
Moreover, in a general configuration, a terminal device is connected to a terminal station device in one-to-one correspondence.
In contrast, in Patent Document 1, a remote radio head, which is a lower-level device, is connected to a terminal station device via a terminal device of a communication system in which a terminal station device is connected to a plurality of terminal devices in one-to-multiple correspondence (see Patent Document 1).
Moreover, LTE and the like use finite frequency resources efficiently by arranging a large number of small cells in an area to achieve a faster data rate and a larger communication capacity. LTE and the like discuss methods of accommodating an upper-level device, a terminal station device, a terminal device, and a lower-level device using a communication system in which a terminal station device and a plurality of terminal devices are connected in one-to-multiple correspondence. A passive optical network (PON) system is an example of a communication system in which a terminal station device and a plurality of terminal devices are connected in one-to-multiple correspondence (see Non-Patent Document 1).
In a mobile radio communication service, strict requirements are set for latency between an upper-level device and a lower-level device for execution of re-transmission control (a hybrid automatic repeat request (HARQ)). Therefore, in Patent Document 1, uplink communication scheduling information of a user device connected to a lower-level device is sequentially transmitted from an upper-level device to a terminal station device, a terminal device, and the lower-level device and the user device is notified thereof. Moreover, a start time and the amount of signal information of uplink communication from the terminal device to the terminal station device are calculated on the basis of the uplink communication scheduling information. In this way, signals of the uplink communication from the lower-level device to the upper-level device according to Patent Document 1 are transmitted with low latency.